This invention relates to power transmissions and, more particularly, to dual countershaft transmissions.
Dual countershaft transmissions, or as they are often termed automatic manual transmissions (AMT), employ mechanical synchronizer clutches whereat full power shifts are available during upshifting of the transmission. The synchronizer clutches, as is well known, establish a synchronous speed between the gear being engaged and the countershaft with which it is rotatably driven. The synchronizer clutches are more costly than a mechanical type jaw clutch or dog clutch, which can be employed in current power transmissions if power interruption during upshifts is permitted. However, since most AMTs desire full power upshifts, the synchronizer clutches are employed in a vast majority of these types of transmissions.
Some single countershaft AMTs permit power interrupted downshifts since during a downshift engine acceleration is expected and desired. These transmissions use jaw-type or dog-type clutches and are not capable of full power upshifts or downshifts.
It is an object of the present invention to provide an improved power shifting dual input transmission having uninterrupted power upshifts.
In one aspect of the present invention, the transmission provides two selectively engageable input clutches, a plurality of mechanical clutches, and a plurality of meshing ratio gears controlled by the mechanical clutches.
In another aspect of the present invention, the even number transmission ratio paths are controlled by one input shaft and one selectively engageable input clutch and the odd number ratio paths are controlled by another selectively engageable input clutch and another input shaft.
In yet another aspect of the present invention, each of the input shafts has operatively connected therewith a selectively engageable brake mechanism.
In yet still another aspect of the present invention, the selectively engageable brake mechanisms are operative to control the speed of the respective input shaft prior to a power upshift interchange